var sha256 = require('js-sha256').sha256;

var Deck = function(get_seed) {
    var used_cards = {};
    var n_used_cards = 0;

    var get_bits = function(seed) {
        var arr = sha256.array(seed);
        var ret = [];
        for (const i of arr) {
            var k = 1;
            for (var p = 0; p < 8; ++p) {
                ret.push(i & k);
                k *= 2;
            }
        }
        return ret;
    };

    var cur_sha = get_bits(get_seed());
    var cur_idx = 0;

    var get_bit = function() {
        if (cur_idx === 256) {
            this.cur_sha = get_bits(get_seed());
            this.cur_idx = 0;
        }
        return this.cur_sha[this.cur_idx];
    }

    this.get_card = function() {
        var rem = 52 - n_used_cards;
        var cur = get_bit();
        var pow = 2;
        while (pow < rem) {
            cur += get_bit() * pow;
            pow *= 2;
        }
        if (cur >= rem) {
            return this.get_card();
        }
        var idx = 0;
        for (var i = 0; i < 52; ++i) {
            while (idx in used_cards) {
                ++idx;
            }
            ++idx;
        }
        while (idx in used_cards) {
            ++idx;
        }
        used_cards[idx] = true;
        ++n_used_cards;
        return to_card(idx);
    }

    var to_card = function(idx) {
        var num = idx % 13;
        var suit = Math.floor(idx / 4);
        return {
            num: num,
            suit: ['diamonds', 'clubs', 'hearts', 'spades'][suit]
        };
    }
};

module.exports = Deck;